1. Field of the Invention
The present invention relates to a current mirror circuit. In particular, the present invention relates to a current mirror circuit having an operating voltage area broadened to a low voltage side.
2. Description of the Related Art
Of current mirror circuits, for example, a current mirror circuit using a MOSFET makes the following settings. That is, it is general to use the MOSFET in a saturation area. However, according to the foregoing settings, the minimum allowable voltage of output voltage is high; for this reason, it is difficult to achieve low voltage with scale-down. In recent years, there has been developed a technique of reducing the minimum allowable voltage of output voltage to operate a current mirror circuit at lower voltage. Specifically, some current mirror circuits using a linear area of MSFET have been proposed. The technique is disclosed in the following document, for example.                Document: O. Charlon, W. Redman-White, “UltraHigh-Compliance CMOS Current Mirrors for Low Voltage Charge Pumps and References”, Proc. Of ESSCIRC 04, pp. 227-230, Leuven (September 2004)        
However, even if the current mirror circuit disclosed in the foregoing document is employed, it is difficult to sufficiently satisfy low voltage requirements under the process rules less than 1.5 μm rule.